feat: 回收站、批量编辑、合并导入与标签治理

- 数据：Task 增加 deletedAt，schema v2→v3；删除改为软删除，保留 30 天后自动清理
- 回收站：支持恢复、永久删除、二次确认清空；导航栏入口带数量角标
- 批量编辑：多选后统一移动列、改优先级、标签增删、设置截止日、归档
- 合并导入：按 id 匹配、updatedAt 新者胜；覆盖/合并二选一，执行前自动快照
- 标签治理：全局重命名、合并、删除；回收站任务不参与改写
- 看板语义读取统一改用 activeTasks，避免已删除任务泄漏到统计、今日与标签下拉
- UI：回收站图标与备份统一尺寸；批量编辑条统一控件高度并分组
- 测试：705 个单测通过，补充迁移、回收站、批量编辑、合并与标签用例

src/components/BoardToolbar.vue

@@ -12,7 +12,12 @@ import TagFilter from './TagFilter.vue'
 
 defineProps<{ hiddenNote?: string; selecting?: boolean }>()
 
-const emit = defineEmits<{ archive: []; 'batch-add': []; 'toggle-select': [] }>()
+const emit = defineEmits<{
+  archive: []
+  'batch-add': []
+  'toggle-select': []
+  'manage-tags': []
+}>()
 
 const store = useTaskStore()
 const filters = useFilterStore()
@@ -24,15 +29,15 @@ const searchRef = ref<HTMLInputElement | null>(null)
 const PRIORITY_ORDER: readonly Priority[] = [3, 2, 1]
 
 const dueTodayCount = computed(
-  () => store.tasks.filter((task) => isDueToday(task.dueDate, task.status)).length,
+  () => store.activeTasks.filter((task) => isDueToday(task.dueDate, task.status)).length,
 )
 
 const overdueCount = computed(
-  () => store.tasks.filter((task) => isOverdue(task.dueDate, task.status)).length,
+  () => store.activeTasks.filter((task) => isOverdue(task.dueDate, task.status)).length,
 )
 
 /** 当前可归档（已完成且超过保留天数）的任务数量 */
-const archivableCount = computed(() => findArchivableTasks(store.tasks).length)
+const archivableCount = computed(() => findArchivableTasks(store.activeTasks).length)
 
 function focusSearch(): void {
   searchRef.value?.focus()
@@ -91,6 +96,7 @@ defineExpose({ focusSearch })
         :selected="tags"
         @toggle="filters.toggleTag($event)"
         @clear="filters.clearTags()"
+        @manage="emit('manage-tags')"
       />
 
       <div class="ml-auto flex items-center gap-1.5">
@@ -129,7 +135,7 @@ defineExpose({ focusSearch })
     </div>
 
     <div class="flex flex-wrap items-center gap-x-2 gap-y-1.5 text-xs text-slate-500 dark:text-zinc-400">
-      <span>共 {{ store.tasks.length }} 个任务</span>
+      <span>共 {{ store.activeTasks.length }} 个任务</span>
       <span v-if="hiddenNote" class="text-slate-400 dark:text-zinc-500">{{ hiddenNote }}</span>
 
       <div class="ml-auto flex items-center gap-1.5">